Automatic toll trunking system



3, 1954 F.- KESSLER ETAL 2,685,617 AUTOMATIC TOLL TRUNKING SYSTEM Original Filed Oct. 16, 1950 9 Sheets-Sheet 1 TOLL BOARD CORD CCT.

r HO- 'IIO+ /T I v I bIAI. RING com COIN RETURN COLLECT q: g O Q '5 I- n m E v MARGINAL 5} I S-IG I m INVENTORS.

FRANK KESSLER BY WILLIAM w. PHARIS ATTORNEY F. KESSLER ET AL AUTOMATIC TOLL TRUNKING SYSTEM Aug. 3, 1954 Original Filed Oct. 16, 1950 9 Sheets-Sheet 2 m B M .5 6 H w w 0 I 2 3 4 5 6 fl v2 2 22a 29/. 4 R I 3 3 C I M V g c 2 R I c F H F H D 3 V v m H LMT- #1 v H M w II. l I I I I ll 1 A H H mm s R m Hi M H T R s r J OUTGOING TRUNK REPEATER FIG.2

ATTORNEY Aug. 3, 1954 v F. KESSLER ET AL. 2,685,617

I AUTOMATIC TOLL TRUNKING SYSTEM Origifial Filed 001;. 16, 1950 1 9 Sheets-Sheet s 4R I rCI5 MW W SLOW OPERATE OUTGOING TRUNK REPEATER FRANK uwggvroks.

. KE LER G- 3 WILLIAM W.PHARIS Byj ATTORNEY I g- 1954 v F. KESSLER ET AL 2,685,617

AUTOMATIC TOLL TRUNKING SYSTEM Original Filed Oct. 16, 1950 9 SheetsSheet 4 LTI INTER- OFFICE 3 TRUNK R6! SLOW I OPERATE 9 .42

lNCOM/NG TRUNK REPEATER INVENTORS.

FRANK KESSLER FIG. 4 By WILLIAM W. PHARIS ATTORNEY Aug. 3; T934 F. KESSLER ET AL AUTOMATIC TOLL TRUNKING SYSTEM Original Filed Oct. 16, 1950 9 Sheets-Sheet 5 (-I INCOMING HS HS 7 I H) TR-UNK REPEATER I I I I SLOW OPERATE I l I I20 I. P. M.

SLOW OPERATE (-H-fi- 3 I I may W M new I \R7 I I ML I I now INVENTORS.

ATTORNEY FIG.5

F. KESSLER ET AL AUTOMATIC TOLL TRUNKING SYSTEM Aug. 3, 1954 '9 Sheets-Sheet 6 Original Filed Oct. 16, 1950 S R 2 I SHS aron 3XON i Z 3 m T V r d x 3 "M. ooooooooo ol o 000000000001 +M W H H E H. m F T 0 Y :2 5 2 S R N W H v T MC H T w OE CL N E l I l I I S N H m H F {IL llll q I H l B c 1% I I I I I 7 I M T/ R s L/ NOTES I. CONNECT M WIRE TO ALL XX LEVELS NOT REQUIRING DIGIT CANCELLING.

2. CONNECT W WIRE TO ALL XX LEVELS INCOMING REPEATER IS TO SWITCH THROUGH.

INVENTORS. FRANK KESSLER WILLIAM W. PHARIS FIG. 6

ATTORNEY Aug. 3, 1954 F. KE'SSLER ET AL I 2,685,617 AUTOMATIC TOLL TRUNKING SYSTEM Original Filed Oct. 16, 1950 9 Sheets-Sheet 7 CONNECTOR ens I CH5 l (-)|ET! i I +--|T 53 I LI (H I \5 I l I IN V EN TORS ATTORNEY Aug. 3, 1954 F. KESSLER ET AL AUTOMATIC TOLL TRUNKING SYSTEM Original Filed Oct. 16, 1950 9 Sheets-Sheet 8 CONNECTOR 2YON R.B.T.

INVENTORS. FRANK KESSLER By WILLIAM W. PHARIS 7. z. w

ATTORNEY FIG.8

Aug. 3, 1954 Original Filed Oct. 16, 1950 LINE CIRCUIT NOTE.

CONNECT (4-) TO HS BANK CONTACT OF EACH PAY STATION L INE.

' KESSLER ET AL 2, 5, 17

AUTOMATIC TOLL TRUNKING SYSTEM 9 Sheets-Sheet 9 r- AUTOMATIC PAY STATION DIAL JIM

ATTORNEY Patented Aug. 3, 1954 AUTOMATIC TOLL TRUNKING SYSTEM Frank Kessler, .Los Angeles, Calif., and William W. Pharis, Rochester, N. Y., assignors to Stromberg-Carlson Company, a corporation of New York Original application October 16, 1950, Serial No'. 190,366; Divided and this application October 41-8, 1951, Serial No. 251,961

12 Claims. 1v

This invention relates to telephone exchange systems employing automatic switching and the objects are to provide improved circuit arrangements forphandling toll calls from a toll board to subscriber's lines in .a dial office. Although the toll board and the automatic switching equipment may be in the same oifice, the present disclosure contemplates the toll board" in one office and'inter-connected to a distant .dial ofiice by means of one-way trunks, one of which is illustrated in the drawings and described in the description; "The present application is a division of the earlier filed application Serial No; 190,366, filed October" 16, 1950, and issued February 16, 195%, as United States Patent No. 2,669,606.

The-main object of the present invention is theprovision of the various enumerated features in atoll switching system in a simple and economical manner A feature of theinvention relates to a novel incoming trunk repeater, terminating a toll line from-a toll board; for connecting the toll line straight through the repeater and cutting the repeat-coilo'f the repeater out ofthecircuit when certain marked levels of the incoming selector, with which the repeater is operatively associated, arese'lected.

Another feature of the invention contem plates a two-Wire inter-office trunk inter-com nectin'gthe toll board and the dial oince, with wet-dry supervision repeated to the toll board under the control of a conductor extending through the automatic switching equipment, which conductoris independent of the talking circuit.-

Still an'other feature of the present invention relatesto a two-speediiash busy and busy tone arrangement, whereby a busy-flash signal at one rate and a busy tone are transmitted to the toll board in response to a call to a busy line, while a=:busy :fiash signal at another rate without the busy'tone is transmitted-to the toll board on a callto' overflow, that is, finding all trunks in a groupfbusy.

Another feature closely related to the last mentioned feature ist-he provision of the flash busy signal by flashing the inter-oifice' trunk with an intermittent wet-dry signal.

An additional feature of the invention comprises a-pplying coin control potential at the toll board to the inter-office trunk, receiving this potential at the incoming trunk circuit in the dial ofilce, repeating the proper-coin control potentialat the incomingtrunk circuit tothe called 2 line by way of the connector switch and switching the called line straight through the connector switch to the trunk circuit.

Still an additional feature of this. invention is the provision of means whereby the toll operator can release theconnection with the interoffice trunk in a dry condition, that is, .nocurrent on the trunk, which is the condition when the called party is onthe line.

A further feature of the inventionrelates to a connector, operated as above mentioned, which will also function to automatically collect the coin at the called station at the timethe connection is released.

An additional feature of the invention is the provision of a line seizure visual signalat the toll operators position to indicate that. the called line has been seized. This feature in the present invention is controlled over the fourth or control conductor in the dial office equipment and by a single reversal of the line current overthe trunk line. A feature closely related to thisarrangement is the single reversal of the trunk to indicate line seizure, with other indications transmitted over the trunk by weted-ry conditions.

,-A still further feature of the invention relates to. operator controlled ringing start and re-ring operations of the connector, :these controls being recorded at the incoming trunk circuit in the dial ,oflice and relayed .to the connector in this oiiice by way .of .a separate control conduccuit repeater associated with .the above men-- tioned outgoing trunk jack, this repeater terminating the illustrated trunk circuit at the toll Figs. 4 and 5 illustrate the incoming trunk circuit repeater which terminates the toll trunk at the dial ofiice.

Fig. v6 illustrates-an incoming selector ,asso-- ciated with-the incoming trunk circuit repeater.

Figs. 7 and 8 illustratev a combination local and toll connector which may be reached from a level of the incoming selector or from a level of a local selector for selecting called line terminals.

Fig. 9 illustrates the connections to an auto matic pay station.

For the purpose of simplifying the illustrations and facilitating the explanation, various parts and circuits constituting the embodiment of the present invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose in mind of making it easy to understand the operation of the circuits than illustrating the specific construction and arrangement of parts that would be employed in practice. For example, the various relays and their contacts are illustrated in a conventional manner with symbols used to indicate the connections with the terminals of batteries or other sources of current, instead of showing all the wiring connections to these terminals. The relays are given reference characters where possible to indicate the mode of operation in the circuit. For example, relay GB is the calling bridge relay, relay RD is the release delay relay, and relay XD is the delay relay following the X operation of the switch. Plus and minus symbols and are employed to indicate the positive and negative terminals respectively of the usual central office common battery instead of using the ground and battery symbols frequently found in telephone circuits, it being understood that the (-l) terminal is connected to ground. The reference characters lH-' and ilii+ refer to coin return and coin collect potentials respectively, it being understood that these connections are common to the illustrated equipment and are used for coin control purposes. The contacts of the various relays are located at various distances from the block representing the winding of the associated relay and those contacts controlled by a relay are indicated as being associated therewith by means of a dashed line.

With this general description of the objects of the invention and the apparatus involved in mind, a detailed description of the operation under various conditions will now be given. It

will be convenient to give several examples of the l circuit operation, such as a toll call to an idle line, delayed ring, ring start, re-ring, etc.

Local call through connector Since the features of the present invention relate to toll connections, it is not believed necessary to describe the detailed operation of the combination connector when used on a local call. It need only be pointed out that the CH8 conductor, leading to the connector, is not terminated at local selector banks. Consequently, there is no operation of the TL relay in th connector on a local call, thus preventing the operation of the RT relay on this type of call until the call is answered. To clarify this operation, it will be later pointed out how the TL relay operates and locks the RT relay in the connector to hold ofi ringing the called line until the operator, on a toll call, rings over the trunk circuit.

Toll call to idle line When the toll operator, in response to a call for a station reached by means of the illustrated inter-omce trunk, plugs into the outgoing trunk jack associated with this trunk, a circuit is closed (ill for relay SL of the cord circuit and relay A of the outgoing trunk circuit which may be traced from lower high resistance winding of relay A, sleeve conductor S, sleeve contacts of jack and plug and winding of relay SL to This circuit is closed in the event that the outgoing trunk jack is directly connected to an outgoing trunk circuit. In some installations there will be one or more selectors interposed between the outgoing trunk jack and the outgoing trunk circuit, in which event the outgoing trunk circuit is not seized until one or more digits are dialed for selecting the outgoing trunk. Where one or more selectors are used, the above-mentioned circuit for relays SL and A are closed when the outgoing trunk circuit repeater is seized, thus operating relay A but, due to its marginal characteristics, relay SL is not operated at this time. When the dial is first turned off normal to transmit the first digit after plugging into the outgoing trunk jack, a circuit is closed for operating dial relay DL which may be traced from make contact of the dial key (operated to permit dialing operations), winding of relay DL, break contact of relay DL, make contact ON of the dial and resistor I8RS to Relay DL locks itself operated over a circuit extending from at the operated dial key, winding and make contact of relay DL to When th dial key is restored at the end of the dialing operation, relay DL releases to disconnect the dial from the cord.

When the outgoing trunk circuit is seized and relay A is operated, an obvious circuit is closed for operating slow acting relay ISA and this relay in turn closes an obvious circuit for operating relay ZSA. The function of these two slow acting relays will be explained in connection with the condition where the toll operator disconnects while the called party is still on the line. Relay A closes a circuit for operating relay L which may be traced from make contact of relay A, break contact of relay F and winding of relay L to With the plug in the jack,

' a circuit is closed for operating relay C of the outgoing trunk repeater which may be traced from winding of relay 0, break contact of relay F, lower left hand winding of the repeat coil RC, ring conductor R, ring contacts of the jack and plug, make contact of relay DL, impulse contacts of the dial and resistor IBRS to Since it is well known how one or more selectors may be operated over a dialing circuit, such as the one illustrated, the selector operation in the originating ofiice will be ignored in connection with this description. With the dial of! normal a circuit is now closed for operating relay B which may be traced from make contact of relay C, winding of relay B, break contact of relay F, upper left hand winding of repeat coil RC, trunk conductor T, contacts of the jack and plug, make contact of relay DL, off normal contacts of the dial and resistor l8RS to Relay B substitutes for the applied at the make contact of relay C for providing a holding circuit for the B relay while relay C repeats the impulses from the dial.

A closed circuit is now provided for the interoffice trunk for operating relay CB of the incoming trunk circuit repeater, this circuit being traced from upper winding of relay CB of the incoming trunk repeater, break contact of relay LS, break contact of relay SR, break contact of relay RGl, resistance R3, break contact of relay CSl, break contact of relay LS, another 5, break contactcf relay LS; rbreak'zcontact pfirelay CH2. tip trunk :conductorilfl, break contact of relay K of the outgoing trunk repeater,:make contact of relay make'contactofrelay B,fblfiaik contact of 'relayiF, mak .contactof relay B, "lower right hand winding of repeatcoilRC, break contact of relay H, break contact of relay K, ring trunk line conductor break contact of relay CT, break contact of relay LS, lower left .hand winding of repeat-coil'RC, break contact'of relay CSI, resistor R4, break contact :of relay 'RLGTII, break contact of relay SR and' lower 'windingof relay CB :to :Relay CB of the incoming trunk repeatercloseswa circuit for operatingrelay'RD which may be traced from break contact of relay CT, make contact of relay CB, break contacto'f relay LS; breakcohtaotcf relay HS and winding of relay RD to The Iinecircuitto-the incoming selector associated with the incoming repeater is now closed for operating relay C301 this selector, this .circuit "being traced from H, overflow contact 20F 0f the incoming selector, break contact of relay -XD, upper winding of relay CB; break contact of relay SW, trunk conductor'T, 'break'contact of relay CT, break contact of relay SW', make contact of relay CB, break contact of relay SW, make contact of relay RD,'break contact of' relay CT, trunk conductor JR, break-contact of relay SW of the selector and 'lower winding of relay CB to Relay-CB-of the selector closes anobvious circuit for operating relay RD and relay RDcloses'a circuit'for operating relay XD which may be traced from (-I--), off normal'contact IXON, make contact of relay RD and lower winding'of relay XD to Relay RD applies to conductor S leadingback to the incoming repeater for holding circuits that will be later described.

The incoming selector shown in Fig. 6 is of the digit canceling type. Since this particular operation of the selector isimmaterialfor an under s'tanding of the present invention, it will not be explained at this time. For a complete understanding of the digit canceling operation, reference is made to Fig. 4 0i copending application Serial No. 149,072 filed March 11, '1950 and assigned to the same assi'gneeas the present 'invention.

The control of the HS conductor leading'from the HSrl'a-y of the incoming trunk and extending through the selector to the connector forms an important feature of the present invention, consequently the circuit conditions of this conductor will be pointed out from time to time as the description progresses. With the circuit operation up to the present point, potential is applied to the HS conductor at both ends, this extending through both windings of the HS relay of the incoming repeater to the 'HS conductor at this repeater, while is applied "to the other end of the HSconductor through resistor: IZRS, overflow contact lOFandbreak contac'tof'relay SW of the selector;

The circuits are'nowin' condition for responding to the digit dialed ioroperating the incoming selector. As the dial. returns to normal, the impulse contacts are intermittently opened for opening up the above described circuit includ.

ingrelay C of the outgoing repeater, thus causing relay C to intermittently release :in response to the dialed impulses. The intermittent release of relay C opensxup the 'abovedescribed circuit including the a-int'eroflice trunk conductors 01 intermittently. releasingrelay CB. 10f. thexinwith the'impulsesof the dialed'digit. The first release of relay'CB of the incoming selector closes a circuit for the X-magnet of this selector which say be traced from break contact of relay CB, make contact of relay RD, make contact of relay XD-and winding ofmagnet X to The upper winding of relay XD is in multiple with the X magnet so that this relay receives -pulses during the stepping of the selector switch and, due to its slow acting characteristics, it remains operated until the termination of the digit at which-time it is released.

Referring back to the incoming repeater, the first release-of relay CB closes a circuit for *operating relay TM- extending from (H, break-contact of relay CT, break contact of relay CB,

break contact of relay LS, make contact of relay R'Dand winding of relay TM to Since relay TM is of the slow release type, it remains operated until the end or" the'digitat which time it is released. Relay TM switches the circuit leading to both winding of the HS relay from +1 to at a makecontact of rclayRD." Since relay HS is differentially connected, this switch from (i) to energizes its lower Winding and its upper winding (by way of the previously described HS conductor) in opposition so-that the HS relay is not operated at this time. This energization of the HS conductor is of no effect in connection with the selector operation but it is eliective when the combination connector is operatedysuchoperation being later described. When relay 'XD of the incoming selector releasesto mark the end of the digit, a circuit is closed for operating relay HA which may be traced from (H, make contact of "relay RD, break contact of relay XD; off normal contact EXGN, wiper and terminal to which conduct'or M is-connected-off normal cOntact- E-YON, winding of relay HA, resistor t ll-ts, break-contact of relay-HA and break contact of magnet Z' to Relay'HA is rendered'fast topper-"- ate because itsznormally closed break contact shortcircuits resistor MRS to provide a high current flow for initially operating relay HA. Relay HA closes a locking circuit for itself en tending'from' make contact of relay RD, break contact-of relay SW, makecontact of relay HA, break contact of magnet Y and winding-of relay to over the previously described circuit. A circuit is now closedfor operating theiY stepping inagnet which may be traced from (t) snake contact of 'reiay' RD, :oreakcontact dtrelay SW, makecon'tact of relayHA and-wind+ ing oiimagnst Yito. (--)i. The operation of magnet. Y opens up the above described circuit to relayHZ-i for lelfecting its release, which in turn opens -uprthe above" described circuit for magnet Y; for; cheating its release. It is not believed necessary to describe the trunk hunting operation of the incoming selector whenbusy trunks are encotmtered, this operation being fully described in the abovementioned application SerialNoplQfitZ.

When the seiector "finds an idle trunk; relay SW is-operated (this relay being primedby :ener gizingfitsflowerwinding byway ofa makeicons tact of relay CB to make it fast operating) over a circuit extending from make contact of relay RD, break contact of relay XD, oil normal contact 2XON, wiper XX and its terminal to which conductor M is connected, off normal contact IYON, upper winding of relay SW, overflow contact 30F, break contact of magnet Y and winding of relay HA to over the previously described circuit. It might be mentioned at this time that relay HA is also rendered fast in its release operation because its break contact inserts resistor lERS in series with its winding, thus reducing the current flow after the relay has operated to a value which is slightly above its holding value. The operation of relay SW switches conductors T and R from the windings of the CB relay to the windings of the CB relay of the selected connector by way of wipers ST and SR and conductors CT and CR, thus releasing relay CB which in turn opens up and releases relay RD. The closure of the CT and CR circuit to the connector operates the CB and RD relays of this connector in a manner presently to be described for extending (4 back over conductor CS and thence by way of wiper SS and a make contact of relay SW to conductor S leading to the incoming repeater for maintaining on this latter conductor during the connection. Relay SW of the selector is locked operated before relay RD of the selector is released, this locking circuit extending from coming back over conductor CS and wiper SS, make contact of relay SW, break contact of relay XD, ofi ncrmal contact ZXON, wiper XX, conductor M, oif normal contact IYON, upper winding of relay SW, overflow contact 30F, break contact of magnet Y and winding of relay HA to (l over over the previously described circuit.

When relay TM of the incoming repeater is released at the termination of the first digit, the

HS conductor is switched back to at this repeater, thus placing potential on both ends of the HS conductor for maintaining this conductor de-energized. This conductor is connected to at the connector, after the connector is seized by the selector, by way of windings of the TL relay in the connector and back contacts of relays SW and AA.

When the connector is seized, the circuit for operating the CB relay of this switch may be traced from upper winding of the CB relay, break contact of relay CS, break contact of relay AB, conductor CT, wiper ST of the selector, make contact of relay SW, conductor T, break contact of relay CT of the incoming repeater, break contact of relay SW, make contact of relay CB, break contact of relay SW, make contact of relay RD, break contact of relay CT, conductor '"R, make contact of relay SW of the selector,

wiper SR, conductor CR, break contact of relay AB of the connector, break contact of relay CS and lower winding of relay CB to Relay CB closes a circuit for operating relay RD extending from break contact of connector release magnet ZM, make contact of relay CB and winding of relay RD to Relay RD connects to master ground conductor MG of the connector for controlling various circuit and relay operations as will be later described. Relay XD of the connector is now operated over a circuit extending from on conductor MG, off normal contact IXON and lower winding of relay XD to this time over a circuit extending from on conductor MG, ofi normal contact 3YON and Relay YD is also operated atlower winding of relay YD to Relay PD is also operated at this time from on conductor MG, ofi" normal contact IYON and lower winding of relay PD to This places the circuits in condition for responding to the tens digit. The operation of the dial for transmitting the impulses of the tens digit is efiective to operate relay B of the outgoing trunk repeater when the dial is off normal and to release relay B when the dial returns to normal, with the impulses transmitted from the impulse contacts of the dial being effective to intermittently release relay C of the outgoing trunk repeater, all in the previously described manner. At each release of relay C the inter-ofiice trunk is opened for releasing relay CB of the incoming trunk circuit, which in turn operates relay TM, with relay RD remaining operated during the digit transmission and with relay TM being released at the end of the digit, all in the previously described manner. Relay CB of the incoming trunk repeater repeats the digital impulses to the connector by intermittently opening the trunk conductors T and R leading from the incoming trunk repeater through the selector to the CB relay of the connector, thus relay CB of the connector is pulsed in response to the tens digit. During this pulsing of the CB relay of the connector, relay RD is not released because of its slow acting characteristics. The first release of relay CB of the connector closes a circuit for the X magnet of this switch for advancing the switch in its X or primary direction, this circuit being traced from break contact of magnet ZM, break contact of relay CB, make contact of relay RD, make contact of relay PD, make contact of relay YD, make contact of relay XD, make contact of relay YD and magnet m to The upper winding of relay X1) is connected in multiple with magnet XM, thus the impulses applied to the X magnet maintain relay XD in its operated position uitil the end of the impulse transmission for the tens digit, at which time relay XD is released.

Since this is a toll call, relay TL of the connector is operated atthe beginning of the tens digit and released at the end of the tens digit. The circuit for operating relay TL may be traced from break contact of relay AA of the connector, break contact of relay SW, lower winding of relay TL (the upper winding being short circuited at this time), conductor Cl-lS, selector wiper SI-IS, make contact of relay SW, conductor HS, break contact of relay CT, upper winding of relay HS of the incoming trunk repeater, make contact of relay TM and make contact of relay RD to This circuit does not operate relay HS of the incoming trunk repeater because it is differentially energized at this time. Relay TL of the connector operates to close a circuit for operating the ringing trip relay which may be traced from on conductor MG, make contact of relay PD, make contact of relay TL and lower winding of relay RT to When relay TL is released by the release of relay TM of the incoming trunk repeater at the termination of the tens digits, relay RT is locked operated over a circuit extending from on conductor MG, break contact of relay TL, make contact and lower winding of relay RT to It will be understood that relay TL of the connector is released at the end of the tens digit because relay TM connects to the HS conductor for deenergizing the lower winding of relay TL.

The units digit is now transmitted, the im- 9 pulses'from thedialloperatingthe C .andB relays of the outgoing trunk repeater in th'evpreviously describedmanner for transmittingthe. unitsdig- .ital impulses over the interoflice trim-k, for impulsing relay CB of; the incoming trunk repeater, for operating: relay Thiat the beginning. of; the digit and for releasing this. relay at the end of the.digit',.all in the previnusly described manner. Relay GB of the. incoming. trunk repeaterpulses the-.T and R conductors leading to relay GB. of theconnector for causingrthis relay to. repeat the pulses of. the units digit. Belay of the con.- nector is again operated, hy. means or" the previously described circuit, at the beginning. of the digitandareleasediat the .end'. of the-digit. "The release ofrelay GBcloses a. circuitriorzoperating the Y or secondary. stepping :magneti which may be :traced from. break contact of magnet 'ZM', break contact. ofirelay: CB, make-contact of relay RD, make contactof relay PD; make contact of relay YD, break contact voftrelay and; winding. of magnet SF-Mi to Theupper winding of relay YDaisconnected in parallelwith magnet YM; .thusmaintaining relay "YD-lira its operated positionuntil :the end of the units digit, at which time relay YD -is released. At the first Y step oi the connector switch, the previously describedoperating circuit-for relay PD is opened but a firstlocking-circuit is closedforthiarelay which may-be traced fromoil-conductor =ma'ke contact l-YON, make contact ofrelay' PD, break contactofrelay SW, breakcontact-of relay XD-andlower winding oi-- relay PD to When relay TL operates at the-beginning-of the-units digit, theabovedescrihed locking circuit i'orrelay -RT is opened hut the previously describedoperating-circuit -mr this relayis closed for maintaining the relay energized until the end or" the units digit, at which time the locking circuit for relay RT isagain closed. I

The station digit is= now transmitted from the dialat the toll operators position, with relays c and-B- of theoutgoing trunk repeater being op- -erated torepeat the impulses of this dig-it over the inter-efiice trunk for causing relay CB of the incoming trunk repeater-to repeat tiiaimpulses over the-trunk conductors-leading to the connector. RelayTM of the incoming trunk repeater is operateclandreleased asbefore for operating-andrelea-sing relay TL of the con- --nector. The release of relayCB-of -the connector at the-beginningcf the first impulse oft-he station-digit closes circuit ior operating-relay extending from break contact of-"magnet ZM, break contact of relay CB, make contact-of relay RD, make'contact of-relay'Pfi -break con- "tact of relay- YD, another breakcontact of relay YD and upper-winding of relay XD' to"(). Relay XD-closes a locking circuitioritselfextench ing from on' conductor-'MG, offno-rma-lcorrtact I-YO'N, make contact of" relay PB; break contact of relay SW, makecontactand-lower-wind ing-oi relay X!) to RelayXDo-pensthe first locking circuit of relay "PD but relay TL (op- 'erated) closes a second locking circuit for relay PD-extending from on conducto-r'MG', make contact of relay TL, make contact and. lower winding of relay PD'to A third locking circuit is closed for relay PD' while relay. CE is released which extends from break contact or -magnet ZM, break-contact of-relay GB, make contact of relay RD, make contact of relay Pl'J, break contact of' relay D and upper windiingzof .re'lay'P-D- ta The -release of relay That'the end ofthe station digitcmsesthe aboVe described locking circuit for relay RT so that this relay remains operated at the end; of this digit. Wit-h relay CB operated, with relay TL released and with relay operated the third, second and firstrlocking, circuits for relayiPD are opened for releasing this relay. The release .of relay PD opens up the above described locking circuitior relay; XD for releasing this relay.

Line seizure Assuming that the called lineris idle, relay SW of: the connector is operated at the. end. of the station digitover a. circuit whichmay be traced from (l-l, makelcontact of relayRD, breakcontact of. relay BI, lcwer winding. of relay .SW, .break contact of relay XD, break contactof relay 'PD, wiper S and terminal ,of the called idle line to through the winding. of-the cut off relay of the called line circuit (notshown) to Relay SW applies to wiper S for making the called, line busy and for operating the cut. ,off relay associated with this. line. Relay SW also closes alocking circuit for itself. extending from on conductor MG, .make. contactandupper winding of. relay SW to When the operatorrestores the-dial'key of the cord circuit, relay BL is released, thus disconnecting fromringconductor Bleadingto the outgoing trunk repeater for releasing relay C. The tip conductor T isalso open atthistime for releasing relay B. When relay SW of the connector operates, the CHS conductor is switched from to for closing .an operating circuitfor relay HS of'the incoming. trunk repeater, .this circuit being traced from break contact of relay .TM, upper winding. of relay HS (the lower winding .of this relay now being short circuited), break contact of relay CT, conductor HS, make contact of relay of the selector, wiper SHS, conductor CHS, both windings of relay TLto. a branch' circuit being now extended through a make contactv of relay SW, a breakcontact of relay AA and-a .makecontact of relayRD -to--(').. This energizesboth windings of relay TL in opposition so that .this relay .is notoperated at this. time. ,Relay LS. of. the incoming trunk repeater is .now operated over a circuit extending froml) on conductor S,.make contact of relay HS and-winding of relay LS to Relay LS-closesalocking circuitforitself extending from on conductor 1S and. av make contact-oi relay LS to the windingof .t'hlf relay, this circuit beingindependentof the make contact of relay.I-IS, thusrholding relay LS operated independent of the operation of the HS relay. Relay SWofthe incoming trunk. repeater is now operatedover a circuit which maybetracedfrom a(+) pulse on thecommon .izfliPM conductor, lowerwinding of relay SW, makecontact of relay HS,-brea-k contactof relay SW and make contact of relay RD to Relay SW closesra locking circuit for itself extending from upper winding of relay SW, make contact of relay SW and make contactof relay RD to The lower winding of rela-ySW is opened at its break contact.

The operation of relay LS of the incoming trunk repeaterreversesthe trunk circuit conductors TT and TR thus reversing the battery back over the-trunk to the outgoing. trunk repeater. The trunk is now-energized by way of a-circuit which may betracedi'rom ,upper winding of relay CB of the incoming trunk repeater, rectifier- RF-l, break-contact of relay SR, break contact ofrela-y RG1, resistor R3, break contact of 1 1 relay CSI, upper left hand winding of repeat coil RC, make contact of relay LS, break contact of relay CT, inter-ofnce trunk conductor TR, break contact of relay K of the outgoing trunk repeater, break contact of relay H, lower right hand Winding of repeat coil RC, break contact and lower winding of relay upper right hand winding of repeat coil RC, break contact of relay B, make contact of relay A, break contact of relay K, tip trunk conductor TT, break contact of relay CT of the incoming trunk repeater, make contact of relay LS, lower left hand winding of epeat coil RC, break contact of relay CS I resistor Rs, break contact of relay RG1, break contact of relay SR and lower winding of relay CB to Relay E of the outgoing trunk repeater was primed by the operation of relay A over a circuit extending from make contact of relay A, resistor 2R and upper Winding of relay E to Now when the current is reversed over the trunk line, as above described, the current flow through the lower winding of relay E is in the proper direction to assist that in its upper winding so that relay E is operated. The operation of relay E closes a make contact which short circuits resistor 2R, thus removing this resistance from the circuit of the upper winding of this relay so that relay E will remain operated by means of its upper winding independent of any current flow through its lower winding. Relay R is inserted in the inter-office trunk circuit when relay E operates and opens up its inner lower break contact for removing the short circuit from the winding of the R relay. Relay F is operated in response to the operation of relay E over a circuit extending from make contact of relay A, make contact of relay E and winding of relay 1*" to The operation of relay F opens up the previously described operating circuit for relay L but this Jrom lowermost break contact of relay N (it being assumed that the X connection instead of the Y connection is used in this circuit), make contact of relay G, break contact of relay J, make contact of relay F and winding of relay P to The operation of relay P closes a circuit from through the low resistance upper winding of relay A to the sleeve conductor leading to the trunk jack and cord circuits, the current flow in this circuit being suificiently high to operate marginal relay SL in the cord circuit for closing an obvious circuit to signal lamp SIG, thus giving the operator a visual signal that the called line has been seized and that ringing may be effected at any time.

Delayed ring These circuits are so arranged that the operator may seize the called line, in the manner just described, hold off the ringing operation until she is ready to signal the called station. This is effective because relay RT of the connector has been operated and looked as previously explained. The operator may leave the connection in this condition and work on the other portion of the toll cord circuit, for example, before ringing the called station. In the event that the called station, or another station on the called line, if it is a party line, removes the receiver,

the operator will get a signal to this effect. This is accomplished because the called line circuit is extended through connector wipers T and R to the windings of relay AB. This circuit may be traced from connector Wiper T, make contact of relay SW, break contact of relay CC, make contact of relay RT, break contact of relay CS, lower winding of relay AB and make contact of relay SW to The circuit from the R wiper extends through a make contact of relay SW, break contact of relay CC, make contact of relay RT, another make contact of relay SW, break contact of relay CS and upper winding of relay AB to Consequently, if a party on the called line removes the receiver, relay AB is operated for closing a circuit for operating relay AA extending from make contact of relay AB, make contact of relay SW and winding of relay AA to Relay AA switches the above described circuit, including conductor CHS, from (at a make contact of relay RD) to at a make contact of relay AA. This means that is applied to both ends of the HS conductor, since relay TM of the incoming trunk repeater is released at this time. Therefore, relay HS of the incoming trunk repeater is released for closing a circuit for operating relay SR extending from (-1-), break contact of relay CT, make contact of relay CB, make contact of relay RD, break contact of relay HS, make contact of relay RD, make contact of relay LS and winding of relay SR to The operation of relay SR disconnects the inter-ofoce trunk conductors from the above described circuit leading to the CB relay. Relay SR places a closed circuit across the CB relay, including resistor Ri, to prevent the release of this relay under this condition. The tip trunk conductor TT may now be traced through a break contact of relay CT, make contact of relay LS, lower left hand winding of repeat coil RC, break contact of relay CSI, resistor R4, break contact of relay RGI, make contact of relay SR, resistor R2, break contact of relay RS, break contact of relay CS, windin of relay RS (high resistance, 6500 ohms, for example) make contact of relay RD, make contact of relay CB and break contact of relay CT to The ring trunk conductor TR may now be traced through a break contact of relay CT, make contact of relay LS, upper left hand winding of repeat coil RC, break contact of relay CSI, resistor R3, make contact of relay LS, winding of relay CS (high resistance, 6500 ohms, for example), resistor R9 and break contact of relay RG to It will thus be seen that the inter-office trunk is switched from a wet to a dry condition when a party removes the receiver on the called line, since the trunk circuit is not energized under this condition, both sides of which extend to through high resistance coils. This dry condition of the inter-oflice trunk effects the release of relay R in the out-going trunk repeater, which in turn opens up and releases relay G which in turn opens up the above described locking circuit for relay L for effecting the release of this relay. Relay L released and relay P released removes from the low resistance winding of relay A, thus inserting the high resistance winding of this relay in the sleeve circuit for releasing relay SL of the cord circuit, which in turn extinguishes lamp SIG to give the operator a visual indication that a subscriber on the called line has removed the receiver. It will be understood that relay A of the outgoing trunk repeater is f3? not ,;releaseda under :thiscondition because. of acircuit through. :itszlower high resistance wind,- ing tQIH-Q. Thezoperatormaulot course, go. in on the connection. and; give: the party on the called: lineothe proper instructions under this condition.

' Ring-start With the circuits in. the condition above described, that is, an idle called line. selected; the operator may start the ringing of; the called station when she ready to signal this station by operating the ring key associated with the cord circuit. This key operation applies through the resistance coil to the ring side of the cord and. jack circuit by way of a break contact of relay DL. This circuit may now be tracedtby way of conductor R, lower left had winding of the repeat coil RC of the outgoing trunk repeater, make contact of relaybreak contact: of, relay firmakecontactiofrelay Eand; winding of relay Kto Relay Kooperat'es and switchesthe inter-oifice. trunk conductors from the; circuit leading into the; outgoing trunk repeater to ground and generator; the generator conductor being connected to@trunk'TR..andkthegroundi C011:- ductor zbeingconnectedsito trunk. This opening of: the-circuit intothe repeater effects the release of relay 'R'but relay G is not released v,be--- cause or a circuit .to; (-Ie); for this relay'at, a make contact of relay'K; RelayiK also applies; a holding circuit to relay Li Theground connected to trunk conductor extends through the previously-described circuits or the incoming trunk repeater :to the lower winding. of relay GB for holding this relay :operatedduring. theringing condition. The generatorv applied to trunk conductor TR: operatesrelay RG. ofithe incoming trunk repeaternover acircuitwhichlmay. be traced from conductor-TR, vbreak; contact; of relay CT, make contact; of." relay LSa-upper left-hand, winding of repeat coil RC, break contact of relay-CS1, resistor R3, makecontactof relay LS, relay RG and" rectifier RF! in multiple, condenser C4, make contact ofrel'ay LS, resistor R4, break contact of relay GSl, lower-left *hand winding of repeat coil RC; make contact of relay LS, breakcontact of relay- CT, conductor and. makecontact of relay'K to-g-roundL This operatesthe RC: relay which in turn closes anobvious circuit for operating relay RGl When ther-inging key at the cord circuit. is restored, relayK releases. for again energizing the operating relay. The release of relay K also disconnects'generatorfrom the trunk circuit for effecting the release of relays RG and RG1 of the incoming trunk repeater. At the time of the-RG1 relay operationthe circuit to the CB relay is openedfor effecting the release of this relay and when relay RGl releases: at the end of theringing signal, relay-"CB is againoperated. Relay TM is also operated over acircuit extend.- ing from make contact of. relay RGI, make contact of relay RDiand winding ofrelay PM to The TM relayis releasedwhenrelay RGI 'releasesto :open up' the above described circuit.

relay RD, thus holding relay Hs operatedby way of its lower winding. This (1 applied tothe HS conductor extendsto the lower winding of relay: Thor the: connector and, since this A relay "114 is. nowunbalanced .iil'IlSsODQllfiitY-i'dlfl')! opening: no the above describedqlocking' circuit. for re'lay RT; thus effecting. the release. of this .relaya. The release of relay TM of; the, incoming "trunk re.- peater,v at the termination oiwthe ringing signal iromzthedistant ofiice,switches:thezl-IS conductor back to forzreleasingrelay'lfhotthecom nector because this energizes both, windings-of this: relay interposition. the, circuit to (--,=)I= 'ex tending through a: make contact of; :relay break; contact. 1oz":v relay AA and: a. make contact of relay 1RD. With. relays. TL and'RT released; the called stationisrun o er-acircuitextendin from. the: common g nerator source GEM MDD winding ofjrelay RT, break contact/of relay TL, break contactz-of'relay R ,:.-break.contactzofmelw .CVC, make contact of relay SW, wiper R, over the called line circuit; wiperT, makeacontactmfztrclay SW, break contact on relay CCan-d break contact of relay R'rto v(41) .At thisr-timeringbaokione is applied to the calling trunk over a..ocircuit;;ex;- tending from theI common. ring back. tone; conductor RBT, make contact. of. relay con:- denser C I16, break contact; of relay RT, condenser Cl; break contact of relay AB; conductor 6R; wiper SR of the. selector; make contact of. relay SW; conductor R, break.v contact of relay -C 'I-,, maketcontact oiirelarltnm k ontact ofrel y SW, r ht. hand windings or repeat -c,oil RC. make Talk and supervision- When, the, calledparty: removes the receiver to answer the, call, r.elayl=t'I v is operated, since the upper winding of this relay isin the signaling circuit connected to thecalled line; Relay RT closes alocking circuit for itself extending-,from on conductor MG, break contactzoi relay TL, make contact and lower. winding of relay RT to; Answering-bridgerelay-AB of: the conenector is now opera-ted over a circuit including the-closed called line circuit, this circuitz'being traced from make contact ofrelay, SW; lower winding of; relay AB; break contact oirelay CS, make contact of relay; RT, break contactof relay -C,C make contact of relay. SW, wiperv T and over the called line and substation circuits. in series, wipei' R,cmake contact of relay SWrbr'eak contact; of relay CC, make contact; of. relay-1H1; make, contact of, relay SW, break contact-.of.:relay CS andupper winding'of relay AB to; It will be noted thatrelayABLreVersesthey. battery back over the trunk.conductors.towtheyselector which is in connection withthis connector; This reverse battery isof no-effectinconnection: with a toll call, since the battery'is extended back through the right hand windings of repeat-,coil RC of-the incoming trunk repeater; withv no relay connected in this circuit. The reverse batteryz'is efiect-ive inconnection with a local call; suchia local call'being by way of a selector (not anirrcoming selector) in another group to which a calling line is -connected which may: requirere vers battery for metering or supervision-couriposes. Relay AB- closes a. circuit ior'operating relay A'Aiof' the connector extendingxfromri eeoi,

relay AA of the connector.

make contact of relay AB, make contact of relay SW and winding of relay AA to Relay AA switches the PS conductor from to at its uppermost make contact. This results in potential being applied to both ends of the HS conductor, since relay TM of the incoming trunk repeater is released at this time. Consequently, relay HS of the incoming trunk repeater is released and relay TL of the connector is released at this time. The release of relay HS of the incoming trunk repeater closes a circuit for operating relay SR which may be traced from break contact of relay CT, make contact of relay CB, make contact of relay RD, break contact of relay HS, make contact of relay RD, make contact of relay LS and winding of relay SR to Relay SR changes the inter-office trunk from a wet to a dry condition by disconnecting the windings of the CB relay of the incoming trunk repeater from the inter-office trunk conductors.

It now becomes necessary to provide a substitute holding circuit for the CB relay of the incoming trunk repeater. This holding circuit may be traced from upper winding of relay CB,'rectifier RFA, make contact of relay SR, resistor R! and lower winding of relay CB to Since the inter-oilice trunk is now in a dry condition (no battery flow over the trunk) relay R in the outgoing trunk repeater is de-energized and released. The release of relay R opens up and releases relay G, which in turn opens up and releases relay-P. Relay M is now operated over a circuit extending from make contact of relay A, make contact of relay E, break contact i of relay G and winding of relay M to Relay M closes an obvious circuit for operating relay N. The release of relay G opens up the above described locking circuit for relay L and, since the operating circuit for the L relay is open at a break contact of relay F, relay L is released. The release of relay L disconnects from the low resistance winding of relay A for providing a high resistance circuit to relay SL of the cord circuit, thus releasing this relay and extinguishing lamp SIG as an indication to the operator that the called party is on the line. The talking circuit is now established, with battery being fed to the called line by way of the AB relay windings of the connector circuit, with the called line circuit being connected to the right hand windings of repeat coil RC of the incoming trunk repeater by way of condensers C5 and C1 of the connector, with the left hand windings of the incoming trunk repeater repeat coil being connected to the inter-omce trunk circuit in the terminating office, with the right hand windings of repeat coil RC of the outgoing trunk repeater beingconnected to the trunk conductors in the originating office and with the left hand windings of the outgoing trunk repeater repeat coil being connected to the toll cord circuit. It will be understood that a toll line circuit may be con nected to the opposite cord (not shown) of the .toll board cord circuit.

When the called party hangs up the receiver, relay AB is released for opening up and releasing The release of relay AA switches'the HS conductor back to at the uppermost make contact of relay RD. Since relay TL is now differentially energized, it will not be operated at this time. Relay HS of the incoming trunk repeater is energized by this switch in potential on the HS conductor. The operation of relay HS opens up and releases relay SR, which in turn re-connects the windings of relay GB of the incoming trunk repeater to the inter-ofiice trunk circuit, thus energizing the inter-office trunk for operating relay R in the outgoing trunk repeater. Relay R closes an obvious circuit for operating relay G, and relay G closes the above described circuit for operating relay P. The operation of relay P applies to the sleeve of the jack and cord circuits by way of the low resistance winding of relay A for operating relay SL of the cord circuit, this relay in turn closing the circuit for lighting lamp SIG as an indication to the operator that the called party has hung up the receiver. The operator of relay G opens up and releases relay M and this relay in turn opens up and releases relay N.

Re-ring The circuits are now in condition for the operator to re-establish the ringing of the called line if so desired. This is brought about in the same manner as the original ringing circuit, previously described. That is, the ringing key applies to the ring side of the outgoing trunk repeater for operating relay K and this relay in turn applies generator to the ring trunk conductor and ground to the tip trunk conductor, the generator operating relay RG of the incoming trunk repeater and the ground holding relay CB of this repeater to prevent release operations of the circuit. Relay RG closes an obvious circuit for operating relay RG! and this relay in turn operates relay TM for switching the HS conductor from to This switch in the HS conductor operates relay TL, in the previously described manner for opening up the locking circuit of relay RT of the connector, thus re-establishing the ringing circuit. The remainder of the circuit operations, supervision and called station response, are the same as previously described.

Release after called party has'htmg up When the operator gets the above described supervision indicating that the called party has hung up the receiver, she may remove the plug from the trunk jack for effecting the release of relay SL of the cord circuit and relay A of the outgoing trunk repeater. This restores the cord circuit to normal and the release of relay A opens up and releases relays ISA and 2SA in sequence. I'he release of relay A also efiects the release of relays E and F by removing from the circuits or these relays at the uppermost make contact of the A relay. The release of relay A also opens up the inter-oiiice trunk circuit for releasing relay R, this relay in turn opening up and releasing relay G. Relay F opens up and releases relay P, thus the outgoing trunk repeater circuits are restored to normal and the inter-office trunk conductors are opened at the originating office.

The opening of the inter-ofiice trunk at the originating oflice releases relay CB of the incoming trunk repeater for opening up and releasing relay RD, this relay in turn opening up and releasing relay SW, thus restoring the incoming trunk repeater circuits to normal. Since relays SW and CB of the incoming trunk repeater are now released, the trunk conductors leading to the connector are de-energized for effecting the release of relays CB and RD of the connector circuit. Relay RD disconnects from conductor MG for releasing relays RT and SW. The

release of relay SW disconnects from connector sleeve wiper S and the switch is released by means of a circuit extending from break contact of relay RD, break contacts in series of relays RT, PS and CC, X and Y off normal contacts ZXON and ZYON and winding of magnet ZM to When the switch is restored to normal, the X and Y on normal contacts are opened for de-energizing magnet ZM, thus restoring the connector circuits to normal.

Relay RD oi the connector disconnects from conductor OS for rendering the connector circuit idle (magnet ZM applies to conductor CS momentarily for protecting the con-- nector circuit until the switch is completely restored to normal) and for releasing relay SW of the incoming selector. The release of relay SW closes an obvious circuit through break contacts of relays RD and SW for releasing the selector switch, thus restoring the selector to normal. connection to normal, conductor HS being connected to (-l) at both ends for controlling operations in the previously described manner in connection with the next call.

Release before called party has hang up From the above description it will be observed that, due to the interomce trunk being dry while the called party is on the line, relay CB of the incoming trunk repeater is energized locally and not over the trunk circuit. This means that some additional arrangement must be provided for releasing the connection under this condition. This release function is provided by the iSA and ESA relays of the outgoing trunk repeater. When the operator takes down the connection under this condition, relay A is released for releasing relays iSA and ZSA in sequence, as previously pointed out. When relay A releases and before relay 2SA has released, is connected to tip trunk conductor TT for operating relay RS of the incoming trunk repeater over a circuit which may be traced from resistor MRS, make contact of relay ESA, break contact of relay A,

break contact of relay K, trunk conductor TT,

break contact of relay CT of the incoming trunk repeater, make contact of relay LS, lower left hand winding of repeat coil RC, break contact of relay CS2, resistor R4, break contact of relay RGl, make contact of relay SR (operated at this time to render the inter-ofice trunk dry), resistor R2, break contact of relay RS, break contact of relay CS, winding of relay RS, make contact of relay RD, make contact of relay CB (held operated through make contacts of relay normal, including the release of relay RS andany other relays of this circuit which are operated at this time. The trunk conductors leading to the selector and connector are opened by the release of relay CB of the incoming trunk repeater for releasing the selector and connector circuits. This trunk circuit leading to the selector and connector circuits is, of course, switched to contacts of the CBrelay, when relay SW is released by the release of relay RD.

This restores all circuits used in the- Switching through operation of incoming trunk repeater In some installations it is required that the inter-oilice trunk conductors be connected straight through to the battery feed circuit of the connector, thus removing repeat coil RC of the incoming trunk repeater from the circuit. On selector levels at Which this operation is required, the Q wire is connected to the terminals of the X wiper of the selector, as indicated by Note 3 on the Fig. 6 drawing. When the selector -witches through to the connector on such a level, the operation of the selector SW relay closes a circuit for operating relay CT of the incoming trunk repeater, this circuit being traced from conductor Q, wiper X, make contact of relay conductor LM and winding of relay CT to Relay CT switches inter-omce trunk conductors TT and TR directly through to trunk conductors T and R leading to the connector by way of the selector wipers. Relay CT opens up the HS conductor for canceling the HS control on a call of this class and it disconnects from the contact of relay CB to prevent the operation of the TM relay on this type of call. It will thus be seen that, on a call of this class, the incoming trunk repeater operates to repeat impulses to the incoming selector but after this selector seizes the connector, all relays of the incoming trunk repeater are de--energized except relay CT so that the inter-office trunk control is now directly to the CB relay of the connector, thus removing all repeat coils in the terminating oidce from the trunk. When the connection is released, the release of the SW relay of the incoming selector opens up and releases relay CT of the incoming trunk repeater for restoring the circuits or this repeater to normal.

Call to busy line It will be recalled that relays PD and XD are released in sequence following the receipt or the station digit by the connector. With relay PD released and before relay XD is released a circuit is closed for operating relay BT extending from on the sleeve terminal of the called busy line, wiper S, break contact of relay PD, make contact of relay XD and winding of relay BT to The opening of the lowermost break contact of relay BT opens up the operating winding of relay SW to prevent the operation of this relay on a call to a busy line. Busy tone is connected back to the calling line over a circuit extending from common busy tone conductor BT, make contact of relay BT, break contact of relay SW, lower winding of relay AB, break contact of relay CS, condenser Ct, break contact of relay AR and over conductor CT and wiper ST of the selector to the repeat coil of the incoming trunk repeater, at which point the tone is repeated to the calling line by means of the induced current from the right hand winding of this coil to the left hand Winding, to which the calling line is connected.

With relay RT of the connector operated, a circuit is closed for intermittently operating relay AA, this circuit extending from the common flash interrupter designated 60 I. P. M., make contact of relay BT, break contact of relay SW and winding of relay AA to Relay AA is intermittently operated for providing a 60 I. P. M. flash to the operator at the toll board. Each operation of relay AA switches the right hand terminals of relay TL of the connector from to at the uppermost make contact of relay RD.

This does not operate relay TL because of its differential connection, but it does operate relay HS of the incoming trunk circuit, consequently relay HS is intermittently operated to repeat the flash interrupter signals from the connector. The first operation of relay HS of the incoming trunk repeater closes a circuit for operating relay SS extending from on conductor S, make contact of relay HS and winding of relay LS to Relay LS is locked operated to on conductor S over a circuit which is independent of the make contact of the HS relay. Relay SW is operated at this time over a circuit extending from on common conductor 120 I. P. M., lower winding of relay SW, make contact of relay HS, break contact of relay SW and make contact of relay RD to Relay SW locks itself operated over a circuit extending from upper winding of relay SW, make contact of relay SW and make contact of relay RD to Relay LS reverses the trunk line conductors extending back to the originating office and relay SW switches the trunk conductors leading to the connector from a circuit including the make contact of relay CB to the right hand windings of repeat coil RC. When relay HS is released, following its first operation, relay SR is operated over a circuit which may be traced from break contact of relay CT, make contact of relay CB, make contact of relay RD, break contact of relay HS, make contact of relay RD, make contact of relay LS and winding of relay SR to At the next operation of relay HS, this SR relay circuit is opened for releasing this relay, consequently relay, consequently relay SR follows the intermittent operations of relay HS.

When relay LS of the incoming trunk repeater reverses the trunk line conductors, relay E is operated and locked in the previously described manner. Relay E inserts the winding of relay R in the trunk circuit for operating this relay and relay F is operated over the previously described circuit including a make contact of relay E. Relay R choses an obvious circuit for operating rclay G and relay G closes a circuit for operating relay P extending from break contact of relay N, make contact of relay G, break contact of relay J, make contact of relay F and winding of relay P to From the above description it will be observed that relay SR of the incoming trunk repeater is intermittently operated for flashing the inter-oflice trunk with intermittent wet and dry conditions. This is effective to intermittently energize relay R of the outgoing trunk circuit for intermittently operating relay G, which in turn efiects the intermittent operation of relay P. Relay P intermittently applies (-l) potential through its uppermost make contact to the low resistance winding of relay A for intermittently operating relay SL of the cord circuit, thus providing an intermittent flash of lamp SIG. Since the busy tone is coming back over the inter-ofiice trunk circuit, the operator receives this tone as well as receiving an intermittent visual indication that the called line is busy by the 60 cycles flash of lamp SIG.

When the operator takes down the connection, relays SL and A are released for releasing all of the equipment in the previously described manner.

Call to busy trunk group It will be assumed that all connectors of the connector group are busy, thus the incoming selector goes to overflow for switching the overflow contacts of the sleector of Fig. 6. Relays SW of the selector is not operated on this call because its upper winding is opened at overflow contact 30F. It will be observed that overflow contact 20F applies busy tone back over conductor T to the incoming trunk repeater, but this circuit is not connected to the repeat coil winding unless relay SW of the repeater is operated. Relay SW does not operate on this call because the 120 I. P. M. pulses operate relay HS over a circuit extending from break contact of relay TM, upper winding of relay HS, break contact of relay CT, conductor HS, break contact of relay SW, overflow contact IUF and resistor I3RS to the 120 I. P. M. pulse source. This same source of pulses is applied to the lower winding of relay SW of the incoming trunk repeater, it being understood that during the intervals between these pulses the 120 I. P. M. common conductor is connected to Consequently, while relay HS is operated by the pulses, relay SW cannot be operated through the make contact of relay HS because is applied to both terminals of the lower winding of relay SW. During the interval between these pulses, the potential on common conductor 120 I. P. M. does not complete a circuit through the lower winding of relay SW because, at this time, relay HS is released for opening up this lowor winding. This means that relay HS will be intermittently operated to provide a 120 I. P. M. signal back to the operators position but the operator will not hear the busy tone because the busy tone circuit is disconnected from the repeat coil of the incoming trunk repeater to which the operators talking circuit is connected. The release of the connection on a call of this class is by the release of relay A, when the operator takes down the connection, for effecting the release of the other portions of the equipment, all in the previously described manner.

Automatic co'in control It will first be assumed that the operator takes down the connection after the called party has hung up the receiver and that the automatic coin collect operation is to be efiected. If the coin is to be returned, the operator applies coin return battery to the called line while the called party still has the receiver ofi the hook, this operation being described later.

In accordance with the note relating to the connection of HS bank terminals of the connector, it will be obvious that relay PS is operated on a call from toll to a paystation line. The circuit may be traced from on the HS terminal associated with the called line, wiper HS, make contact of relay SW, make contact of relay TL and winding of relay PS to Relay PS locks itself operated over a circuit extending from on conductor MG, ofi" normal contact EYON, break contact of relay PD, make contact and winding of relay PS to With the receiver at the called station hung up, relays AB and AA are in their de-energized conditions, consequently from the make contact of relay RD is 65(- tended through break contact of relay AA and make contact of relay SW to both windings of relay TL to the HS conductor and, since this conductor is connected to at the break contact of relay TM of the incoming trunk repeater, the HS conductor is energized but relay TL of the connector is not operated because of its differential connections. Relay HS of the incoming trunk repeater is operated because its lower winding is short circuited and its upper winding is energized.

the previously described wet supervision. When the connection is released, in the previously de scribed manner, when the operator takes down the connection, relays CB and RD of the connector are released. "Relay RD disconnects from conductor MG but relay PS maintains on this conductor by way of a circuit extending through make contacts of relays PS and SW. This same circuit locks all or the relays operated which were previously locked to the MG conductor. Since the release magnet of the connector switch is open at a break contact of relay PS, the switch is not released. The release of relay RD disconnects from sleeve conductor CS so that the selector and incoming trunk repeater circuits are restored to normal.

Coin collect relay CC is nOw Operated over a circuit which may be traced from break contact of relay RD, break contact of relay AA, break contact of relay YD, make contact of relay PS and winding of relay CC to Relay CC closes a first locking circuit for itself extending from make contacts in series of relay PS, make contact and winding of relay CC to i is is now ap lied to the called line f r operating the coin collect apparatus at the substation on this line, this circuit being traced from HEN-H, lamp iML, make contact of relay PS, make contact of relay CC, make contact of relay SW and wiper R to the ring side of the called line. This same circuit is extended by way of another make contact of relay CC and another make contact of relay SW to the tip side .of the called line. Relay YD is now operated over a circuit extending from make contact of relay CC, make contact of relay PS and lower winding of relay YD to Relay YD closes a circuit for operating relay PD which may be traced from make contact of relay CC, make contact of relay YD and lower winding of relay PD to Relay PD opens up the above described locking circuit for relay PS for eiiecting the release of this relay. The release of relay PS .opens up the above described first locking circuit for relay CC but before this happens a second locking circuit is closed for relay CC by the operation of relay PD, this locking circuit being traced from on conductor MG, off normal contact IYON, make contact of relay PD, make contact and winding of relay CC to The release .of relay PS opens up the above described circuit for relay YD, this relay releases and opens up and releases relay PD, this relay in turn opening up the above described second locking circuit for relay CC for effecting the release of this latter relay. The release of relay CC removes from conductor MG, which is effective to release relays RT and SW, the latter relay disconnecting from sleeve wiper S. With relays CC, PS, RT and RD released, the release magnet circuit is closed for restoringthe connector switch to normal. It will be obvious that i I 0(+) is disconnected from the called line by the release of relays PD and PS.

in the event that the operator takes down the connection before the called party hangs up, then relays AR and AA are in their operated positions. This connects to the HS conductor through the lower winding of relay TL at the connector and, since is connected to the HS conductor through both windings of relay HS of the incoming trunk circuit, the HS lead is de-energizod and neither relay TL nor relay HS will be operated. Relays CB and RD are released as before, with relay RD disconnecting from conductor MG,

but at this time relay PS is operated for maintaining on conductor MG. The release of relay RD removes from conductor CS for releasing the preceding circuits in the previously described manner and it also closes a circuit at this time for operating relay YD which may be traced from break contact of relay RD, make contact of relay AA .and lower winding of relay YD to The circuits stay in this condition until the called party hangs up, at which time relays AB and AA are released. With relay YD operated and with relay AA operated, is re-applied to conductor CS for holding this connector busy until the called party releases. This circuit may be traced from make contact of relay YD and make contact of relay AA to conductor CS. Now when relay AA is released, this circuit is opened for rendering the connector circuit idle and again selectable.

Recalling that relay PS is locked operated at this time, it will be observed that is applied through its lowermost make contact, by way of a make contact of relay SW, to conductor MG for holding the connector circuits in condition for coin control operation. Now when relay AA is released by the called party hanging up the receiver, the above described circuit to relay YD is opened and, since relay CC is not yet operated, the YD relay is released. A circuit is now closed for operating relay CC which may be traced from break contact of relay RD, break contact of relay AA, break contact of relay YD, make contact oi relay PS and winding of relay CC to Relay CC closes the previously described first locking circuit for itself and it applies H0(+) to the called line in the previously described manner. Relays YD and PD are again operated for opening up and releasing relay PS, with this relay opening up and releasing relays YD and PD in sequence, all as previously explained. Relay CC is looked operated by means of its second locking circuit when relay PD operates and when relay PD releases, this second locking circuit is opened for releasing relay CC. This disconnects from conductor MG for releasing relays RT and SW, the switch being restored to normal in the previously described manner. The release of relays PD and PS disconnects HG(+) from the called line, thus restoring the circuits to normal.

Manual coin control This is a case where the operator desires to collect or return the coin at the called paystation while the called party is still on the line. With the circuits in this condition, relays CB, RD, AB and AA of the connector, as well as various other relays, previously explained, are in their operated conditions. The operator applies Ho(+) or ilil() to the tip side of the cord and outgoing trunk circuit by means of the coin .collect or coin return key. coin potential is extended by way of conductor T, upper left hand winding of repeat coil RC of the outgoing trunk repeater, make contact of relay F, winding of relay D, resistor 1R and break contact of relay L to Relay D operates and closes an obvious circuit for operating relay H. It will be obvious that relays A, E and F of the outgoing trunk repeater are operated, relay R not being operated because relay SR of the incoming trunk repeater is operated with the called party on the line for maintaining the inter-office trunk in a dry condition.

With relay H operated, is applied to the inter-office tip trunk conductor IT by way of a break contact of relay K. At the first energize- 

